A III-V group nitride semiconductor has been variously used for an optical device such as blue/green light emitting diodes (LEDs), a high speed switching device such as a metal semiconductor field effect transistor (MOSFET) and a hetero junction filed effect transistor (HEMT), a light source of an illumination or a display apparatus, and the like. In particular, a light emitting device using an III group nitride semiconductor has a direct transition-type bandgap corresponding to the range of visible rays to ultraviolet rays, and can perform high efficient light emission
The nitride semiconductor has been mainly utilized as a LED or a laser diode (LD), and research for improving the manufacturing process or light efficiency has been conducted.